"There's no significant reduction in Hamilton as there has been in the CBD," he explains.

"The measures introduced in Hamilton have not been effective."

While 14 hotels in the city centre were required to close by 3.30am, Hamilton simply introduced a 1am lockout.

Professor Kypri says the earlier closing times are the key to reducing assaults, with evidence from many studies backing this up.

"Lockouts are a uniquely Australian and New Zealand phenomenon, which haven't been introduced in other places," he says.

"The better quality studies suggest that they don't affect the assault rate."

As for what more Newcastle could be doing, Professor Kypri says clearing people from the area after pubs close is crucial, but also costly as it requires better public transport and an increased police presence.

The professor concedes that earlier closing times and lockouts do affect the "night-time economy".

"What's missing here is a proper discussion of who bears the cost of this," he says.

He points out that the cost to the community of caring for someone with a serious head injury is significant.

"For each hour of trading after midnight the cost is massive, because all you need is a couple of young people to be knocked out, and when they don't die it's more costly.

"Because you've got to look after someone for possibly the rest of their lives."

As for Sydney introducing similar measures, which were given their first real test during the weekend's Mardi Gras, Professor Kypri says they're a "step in the right direction."

However he says excluding assault "hot spots" such as Darling Harbour and Oxford St from the earlier closing times will make the restrictions less effective.